Field of the Invention
The present invention relates to a control apparatus and control method for a motor provided with a position detection unit, and to a technology for enhancing motor drive efficiency.
Description of the Related Art
A stepping motor has features such as compact size, high torque, and long life, and enables easy implementation of digital positioning operations by open-loop control. Thus, it is widely used in equipment such as imaging devices, optical disk devices, printers, and projectors. However, step-out occurs when large loads are imposed on the stepping motor or during high-speed rotation. In order to solve this situation, prevention methods that an encoder is attached to the stepping motor and the energization is switched in accordance with a detected position of the rotor, i.e. brushless DC motor operation is performed have previously been performed.
Japanese Patent Laid-Open No. 2002-119089 discloses a method that high speed and high torque are realized while preventing step-out by using an encoder signal that outputs an output signal according to rotation of a rotor in the stepping motor and by efficiently applying a square-wave drive waveform to the magnetic phase of the rotor.
On the other hand, with respect to conventional brushless motors, a technology that the motor is actually rotated in forward direction and reverse direction after completion of assembly so as to measure motor properties in each direction and that measurement results of motor properties is compared so as to adjust a physical position of a rotational position sensor is known. Moreover, Japanese Patent Laid-Open No. 2005-12955 discloses a method that the rotor of the brushless motor is rotated by using a separate external power source and that a phase difference of an electromotive force signal generated by a motor coil and an encoder output signal is compared so as to detect an amount of physical position deviation of the encoder.
Japanese Patent Laid-Open No. 2004-348227 discloses a method that with respect to a stepping motor, a moving position is corrected so that the motor is again driven to the target position when the position of the motor does not reached the target position, after a drive signal for driving to a target position is input.
However, in the prior art technologies, because a square-wave drive waveform is used and the drive waveform includes harmonic components, a large amount of noise is occurred. Moreover, with a square-wave drive waveform, the accuracy of the stopping position of the stepping motor is poor.
In Conventional brushless motors, it is required that the speed is measured while brushless driving is conducted and deviations of the position are adjusted from the measurement results to thereby take many time. Moreover, in the conventional technology disclosed in Japanese Patent Laid-Open No. 2005-12955, it is impossible to adjust after the brushless motor has been incorporated into the equipment to be driven. Setting operations are difficult for adjustment, because the rotor unit required to be exposed to the exterior in order to connect the rotor to an external power source.
With conventional methods for correcting moving position, positional determination is performed after temporarily stopping the motor, after which the correction operation is performed. Thus, it takes long time for moving to the target position including static stoppage time and the like.